Equalizers in the electrical domain to mitigate various impairments in digital optical communication systems are well known. An equalizer in the optical domain has been proposed but not demonstrated. This proposed equalizer is a multistage lattice filter with many adjustable phase parameters, the parameters chosen by complicated optimization algorithms and compensates only one wavelength channel at a time. There have been demonstrations of single impairment optical compensators, such as chromatic dispersion (CD) compensators and polarization-mode dispersion (PMD) compensators, but these address only one source of impairment at a time.
What is desired is a simple multi-channel optical equalizer for intersymbol interference mitigation which can compensate many wavelength channels of a multiwavelength signal simultaneously and which requires few adjustable parameters.